The invention provides simple and economic methods to isolate glycoproteins (containing mucin, including MUC1) from whey or whey byproducts for the food, pharmaceutical, cosmetic, and other industries. The invention enables a simple recovery of glycoprotein concentrates having excellent thermal stability and solution clarity from whey recovered from cheese production from bovine milk.
Glycoproteins have received attention as a functional additive in various health care and other formulations. It has, for example proved useful as a lubricant in eye care compositions.
The production of cheese from bovine milk results in the production of large amounts of whey. Liquid whey is a complex mixture of protein, fat and salt components in various physical forms and typically has a total solids content of around 6% and contains about 94% water. Lactose can typically be present at a concentration above 4%, lactic acid about 0.2%, ash about 0.5% and fat about 0.15%. Whey protein (total nitrogen times 6.38) is under 1%. The separation of the glycoprotein components from whey, while maintaining recovery of other useful components, presents a technical challenge. Doing this on a large, commercial scale presents an even greater challenge.
Whey is useful in all of its forms. In some cases whey is processed to directly recover whey protein and leaves behind a material often referred to as deproteinized whey, which refers to the liquid remaining after treatment of whey to remove the majority of the whey protein. The material is not deproteinized completely, but contains most of the insoluble membrane protein fragments from milk fat globular membrane (MFGM) originally present in the whey. When produced by some procedures, the fat content is essentially removed. In others, such as ion exchange chromatography, the fat is not removed and is carried along with the deproteinized whey and contains proteins associated with the fat. This fraction contains most of the insoluble membrane fragments.
Bovine MFGM contains considerable amounts of glycoproteins including mucins such as MUC1 and other glycoproteins useful in a variety of food, pharmaceutical, cosmetic, and other products. There are at least five glycoproteins associated with MFGM that can be seen on SDS-gel and can also be detected in membrane concentrated whey. They are MUC1, PASIII, CD36, BTN, and PAS 6/7 according to Mather (2000).
The recovery of glycoproteins could be improved for many applications by providing solutions with high purity, clarity, stability in the presence of salt (e.g., for isotonic or buffered solutions) and heat stability. Accordingly, there is a need for a process that can recover and purify and isolate the various glycoproteins, especially in stable forms for applications requiring either dry or solution formulations.
It is an objective of the invention to provide methodology suitable for obtaining useful glycoproteins containing mucin, including MUC1, from whey.
It is another object of the invention to enable the production of glycoproteins in suitable quantities and of suitable quality for supply to the food, pharmaceutical, cosmetic, and other industries.
It is another object of the invention to improve the overall cheese making process by recovering valuable glycoproteins from whey in a manner that permits most whey protein to be separated from the whey prior to concentrating and recovering glycoproteins from bovine MFGM present in the whey.
It is another object of the invention to provide a simple process that produces glycoprotein concentrates suitable for a variety of uses requiring stability.
It is another, specific object of the invention to provide a simple process that produces glycoprotein concentrates that can be packaged as sterile, clear liquids.
It is another object of the invention to provide a simple process that produces glycoprotein concentrates suitable for a variety of uses requiring stability in solution form that can undergo autoclaving to achieve sterility.
These and other objects are accomplished by the present invention by several procedures.
In one aspect, purified glycoprotein fractions are separated from bovine whey, by: diluting microfiltered deproteinized whey protein to solubilize lactose and mineral salts; heating the resulting diluted aqueous micro-filtered deproteinized whey protein to coagulate heat-sensitive whey protein; cooling the resulting heated solution to precipitate coagulated whey protein; and centrifuging the resulting cooled solution and separating resulting supernatant containing glycoproteins from fat and precipitate.
The product glycoprotein concentrate can be dried, such as by freeze drying, or recovered and stored in liquid form. In a preferred aspect, saline is employed to dilute the microfiltered concentrate prior to heating to improve the recovery of a liquid glycoprotein fraction that can be sterilized, such as by autoclaving. In another aspect, glycoprotein free of a majority of glycomacropeptides (GMP) can be recovered by adjusting the solution to alkaline pH and subjecting to ion exchange extraction.
Some preferred aspects of the invention are set forth below and in the attached flow diagrams.